Make documentation clearer for Windows users: state when descriptions

apply only to Unix; add links to Windows and TPF instructions. Where
defaults are different in OS/2 or Windows, show them.  Add the -k command
line option (Windows only).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@82409 13f79535-47bb-0310-9956-ffa450edef68